Knuckle or articulating joints in power tools are well known and have been used to provide an articulating body arranged such that a handle portion of the tool's body can pivot about a point or axis on the motor housing portion of the tool's body. The pivoting axis is typically along a common mating plane of the two portions of the tool's body. Such a system is exemplified in U.S. Pat. No. 6,364,033 which describes a portable electric tool having an elongate housing which includes two housing members pivotally connected to one another. A locking mechanism is provided for adjustably positioning the second housing member relative to the first housing member. The mechanism includes a pin disposed in a passage, biased against a spring, and which is shiftable between a locking and unlocking position. A locking member is adapted to shift the pin between a locking and unlocking position. This arrangement provides a knuckle joint locking mechanism which is actuated from one side of the power tool housing.
U.S. Pat. No. 5,867,911 describes an apparatus for adjusting relative positions of first and second members. The apparatus comprises two buttons each with two sets of teeth and which are moveable between respective first and second positions. When in a first position, both sets of teeth engage with other sets of teeth carried by the first and second members to prevent relative movement of the first and second members. When in a second position, one set of teeth carried by the button disengages one set of teeth carried by one of the first and second members to allow relative movement thereof. This arrangement has two actuating buttons disposed on either side of the knuckle joint, and both buttons have to be moved or ‘pinched together’ (compressed inwardly) in order to allow relative movement of the first and second members.
Many other forms of knuckle joint are known. For instance, U.S. Pat. No. 2,921,773, U.S. Pat. No. 4,929,113 and U.S. Pat. No. 5,358,352 describe a knuckle joint locking mechanism which is actuated by pressing a button disposed on one side of the joint. Furthermore, U.S. Pat. No. 5,197,817 describes a locking mechanism for a gimbal joint which has a pair of actuator buttons disposed on either side of the gimbal joint, both of which have to be depressed in order to unlock the joint and allow the joint to articulate.
Referring to FIG. 1, a schematic of Black and Decker's™ KC9036 3.6V cordless screwdriver's articulating joint 10 is shown. The joint is arranged to allow relative movement between first 12 and second 14 portions of the screwdriver's body 16. The second portion of the body extends inside first portion in the region of the knuckle joint. The first and second portions pivot with respect to one another about the axis A as indicated by arrow Z. A locking mechanism comprises a first 20 and second 22 sliding cog. Each cog has toothed portions 24 and 26 respectively, and these are held together by a screw fitting 23 passing through the second cog to engage with the first cog. The first and second body portions also comprise toothed portions 30 and 32 respectively. A spring 28 provides a biasing force to maintain the locking mechanism in a locked position, as is shown in FIG. 1. The spring is held between a body portion and the first sliding cog.
In the locked position the toothed portions 24 and 26 of the locking mechanism mesh with both the toothed portions 30 and 32 of the first and second body parts, 12 and 14 respectively. Thus, the first and second body parts are locked to prevent relative movement therebetween; the articulating joint is locked. In order to unlock the articulating joint, the first cog is pressed into the joint, as indicated by arrow B. A portion of the first cog's toothed portion 24 is disengaged from the screwdriver body's first portion's toothed portion 30. Likewise, a portion of the second cog's toothed portion 26 is disengaged from the screwdriver body's second portion's toothed portion 32. The spring 28 is compressed as a result, between an inner face 33 of the first cog and an inner face 34 of the second body portion. Relative rotational movement is thus permitted between the first and second body portions. The locking mechanism returns to the locking position by releasing pressing force on the first cog (as indicated by B) and when teeth in toothed portion 30 and 32 are radially coincident, so that the cogs can return to the locking position.
The prior art provides a mechanism which can be actuated from just one side of the articulating joint, or by pressing a pair of locking buttons into the joint at the same time. The typical single button operated knuckle joint usually has the button for releasing the locking mechanism disposed on the side of the tool which is most convenient for a right-handed user to depress the button with their thumb whilst gripping the tool.
Embodiments of the present invention aim to provide an improved knuckle joint and locking mechanism. In brief, embodiments of the present invention provide a knuckle joint and locking mechanism which can be actuated from either one side or the other side of the joint.